In these days, with phacoemulsification and the like prevailing, an intraocular lens available for being inserted from a small incision, namely a foldable intraocular lens made of a soft material such as silicone, soft acrylic, or hydrogel, has been developed and used widely in clinical practice with an aim to reduce postoperative astigmatism and realize minimally invasive surgery.
On the other hand, there have also been developed a variety of intraocular lens inserting devices as a surgical instrument for inserting such foldable intraocular lens into an eye from an even smaller incision. According to such intraocular lens inserting devices, a folded intraocular lens can be pushed out into an eye through a tubular cylindrical insertion portion, thereby allowing the intraocular lens to be inserted into an eye from a substantially smaller incision compared to using conventional methods which use a pair of tweezers to insert an intraocular lens into an eye.
Such intraocular lens inserting devices are classified broadly into two types: one is a screwed type (screw-in type); the other is a push-in type.
The push-in type is one type of an intraocular lens inserting device in which an operator presses an operational portion of the device against a resistance such as a friction between an intraocular lens and the inner wall of a cylindrical insertion portion, and the pressure applied at that time is transferred to the intraocular lens, thereby advancing the intraocular lens (For example, see Patent Documents 1, 2 and 3). According to these push-in type intraocular lens inserting devices, operation for inserting the intraocular lens is simple and possible with one hand. Thus, the push-in type intraocular lens inserting device has the advantage that an operator can perform another operation with his/her other hand during the insertion operation. On the other hand, the push-in type intraocular lens inserting devices have such a problem that it is comparatively difficult to control an operational pressure applied to push the operational portion because the operator has to move the intraocular lens forward while keeping the balance between the friction of the intraocular lens with the inner wall of the cylindrical insertion portion and the operational pressure of the operational portion. Further, since a nozzle provided on the leading end of the intraocular lens inserting device is generally the thinnest part of the cylindrical insertion portion the intraocular lens passes through, a load applied to the intraocular lens becomes large when a high-degree thick intraocular lens is released from the nozzle or when an inner diameter of a nozzle is made smaller in order to match a smaller incision, thus leading to the possibilities that the intraocular lens may be unexpectedly released into an eye to thereby damage an ocular tissue.
As for a screwed type intraocular lens inserting device, the relation between its plunger and main body is similar to that between a male screw and a female screw, and an operational portion provided at one end of the plunger is rotated, thus moving the plunger, or a rod for pushing out the intraocular lens, toward the lens advancing direction, thereby advancing the intraocular lens (For example, see Patent Document 4). According to these screwed type intraocular lens inserting devices, travel distance of the plunger or rod can be easily controlled, and thus it has the advantage of being able to prevent the intraocular lens from being unexpectedly released into an eye even in the case that a load applied when the intraocular lens passes through the nozzle becomes large, such as when the intraocular lens with a thick optical portion is released, or the nozzle is formed to have a smaller inner diameter. On the other hand, the screwed type intraocular lens inserting device requires the inserting operation to be performed with both hands, and thus there are concerns that an operation of the device becomes somewhat intricate compared to the push-in type intraocular lens inserting device.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-516487
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2003-144480
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2004-351196
Patent Document 4: Japanese Unexamined Patent Application Publication No. H11-506357